The present invention relates in general to computer-aided drawing systems and in particular to a method and apparatus for structuring data acquired by vectorizing a drawing so that such data may be accessed and manipulated by a computer-aided drawing or design system.
Computer-aided drawing or design (CAD) systems permit users to create and modify drawings formed on a CRT screen, and to store and retrieve data which may be used to recreate the drawing either on the CRT or on paper using a hard copy graphics output device such as a plotter or a printer. In the prior art, attempts have been made to improve the usefulness of CAD systems by providing digitizing means to convert a drawing on paper to a set of representative data compatible with the data used by a CAD system, permitting the CAD system to use the data to store, modify and reprint the original or modified drawing.
One such digitizing means is the automatic picture coding system described in prior U.S. application Ser. No. 624,434, filed June 24, 1984, by Benjamin E. McCann and Michael L. Rieger for "Method of Pixel to Vector Conversion in an Automatic Picture Coding System", wherein a bit-map image or the drawing is created by a scanning means such as a facsimile drum scanner, and then encoded into a set of representative line segments which are converted into vectorial representations compatible with the data used by many CAD systems.
While this raw vectorial data representing the drawing may be in a CAD system compatible form, the image recreated by the CAD system using it will generally not be structured in a way that can be easily manipulated by the CAD system. For instance, the drawing image may contain irrelevant marks or stains appearing on the original drawing along with erroneous inclusions or omissions resulting from inaccuracies in the digitizing process. Operators can sometimes use CAD systems to restructure the raw vectorial data correcting these problems but CAD systems are typically designed to operate on images created by the systems themselves and use of the CAD system itself to restructure the data can be time consuming and sometimes ineffectual.
Therefore what is needed is a method and apparatus for receiving raw vectorial data produced by a digitizing means and allowing an operator to quickly and easily restructure the data in a structural form compatible with a CAD system.